Case-hardened bar or plate



NITED STATES JAMES II. VAN DORN,

OF CLEVELAND, OHIO.

CASE-HARDENED BAR OR PLATE.

SPECIFICATION forming part of Letters Patent No. 440,978, dated November18, 1890. Application filed November 26, 1889. Serial No. 331,688. (Nomodel.)

To all whom it may concern:

Be it known that I, JAMES H. VAN DORN, of Cleveland, in the county ofCuyahoga and State of Ohio, have invented a certain new and usefulImproved CaseJ-Iardened lWIetal Bar or Plate as an Article ofManufacture; and I do hereby declare the following to be a full, clear,and exact description of the invention, such as will enable othersskilled in the art to which it pertains to make and use the same.

My invention relates to an improved casehardened metal bar or plate, thesame being adapted more especially for prison work, such bar beingcompressed by rolling or drawing cold, or by other means, whereby a harddense shell is formed as a preparatory step for the case-hardening. Softsteel or iron bars are preferable for prison work on account of theirtensile strength, and to me vent such bars from being readily sawed orout they are usually case-hardened. 1f the case-hardening is deep, itrenders the bar brittle and easily broken, and consequently worthlessfor such purpose. On the other hand, if the case-hardening is of littledepth, such case-hardened shell is easily broken by reason of its havinginsufficient backing. It is not therefore a diificult matter to breakthe thin case-hardened shell of a softmetal bar by means of a sharp blowdelivered with a hammer or other blunt tool, whereby such shell isdriven into the soft metal beneath. Under such conditions by means of afew well-directed blows and by exercising a little of the patience andperseverance for which prisonersunder such circumstances are noted, inpicking out the broken fragments of the case=hardened shell the softmetal of the bar may be exposed, after which the bar can be sawed or outwithout much difficulty.

In carrying out my invention I select tough strong bars, usually of softsteel or iron and a trifle larger in size than is required for thefinished bar. These bars I compress, usually by means of cold-rolling orcold-drawing, to form ahard dense shell, after which the bars arecase-hardened in the usual manner. The compression of the metal intosuch hard shell does not reduce the strength of the bar, and the shellso formed serves two purposes first, it prevents the case-hardening frompenetrating too far into the metal, and, second, this compressed shellconstitutes such a firm backing for the case-hardening that it isdifficult, if not impossible, with any means that a prisoner is likelyto have at hand to indent such bar or break the case-hardened shell.

What I claim is- An improved bar or plate compressed by .cold rolling ordrawing and subsequently case-hardened.

In testimony whereof I sign this specification,in the presence of twowitnesses, this 5th day of November, 1889.

JAMES H. VAN DORN.

Witnesses:

C. H. DORER, ALBERT E. LYNCH.

